Healthy leg veins contain valves that allow blood to move in one direction from the lower limbs toward the heart. These valves open when blood is flowing toward the heart, and close to prevent venous reflux, or the backward flow of blood. When veins weaken and become enlarged, their valves cannot close properly, which leads to venous reflux and impaired drainage of venous blood from the legs. Venous reflux is most common in the superficial veins. The largest superficial vein is the great saphenous vein (GSV), which runs from the top of the foot to the groin, where it terminates at the saphenofemoral junction. There are veins which lead from the superficial veins (great and small saphenous veins, (GSV, SSV, respectively) and “perforate” the fascia and join with a deep vein. Like the GSV and SSV, these perforator veins can become diseased and experience reflux. This could compound the general symptoms of venous reflux, creating additional venous hypertension throughout the region where the perforator is located. These sites are often associated with skin degradation leading to venous stasis ulcers.
Factors that contribute to venous reflux disease include female gender, heredity, obesity, lack of physical activity, multiple pregnancies, age, past history of blood clots in the legs and professions that involve long periods of standing. According to population studies, the prevalence of visible tortuous varicose veins, a common indicator of venous reflux disease, is up to 15% for adult men and 25% for adult women. A clinical registry of over 1,000 patients shows that the average age of patients treated for venous reflux is 48 and over 75% of the patients are women.
Venous reflux can be classified as either asymptomatic or symptomatic, depending on the degree of severity. Symptomatic venous reflux disease is a more advanced stage of the disease and can have a profound impact on the patient's quality of life. People with symptomatic venous reflux disease may seek treatment due to a combination of symptoms and signs, which may include leg pain and swelling, painful varicose veins, skin changes such as discoloration, inflammation and open skin ulcers in the lower legs.
A primary goal of treating symptomatic venous reflux is to eliminate the reflux at its source, such as, for example, the great saphenous vein. If a diseased vein is either closed or removed, blood can automatically reroute into other veins without any negative consequences to the patient. The perforator veins of the leg can, however, still be the source of symptoms despite GSV or SSV occlusion. The most common perforating veins that account for the condition are found in the medial aspect of the lower leg. These were traditionally termed the Cockett's (lower leg), Boyd's (knee region), Dodd's and Hunterian (thigh) perforators. New naming conventions assign names of given perforating veins of the leg as to their location; e.g., tibial, paratibial, patellar, etc. as described further below.
Current non-invasive methods for treatment of reflux in the perforating veins include thermal ablative techniques such as, e.g., radiofrequency (RF) and laser ablation. Sclerotherapy, including foam sclerotherapy, is used as well. Radiofrequency and laser ablation often require tumescent anesthesia which produces both bruising and pain along the treatment zone for several days post-procedure. Both can have side effects such as burns and nerve damage, each of which can result in paresthesia or hypoesthesia. Radiofrequency and laser ablation also can require expensive radiofrequency devices and/or laser boxes in addition to expensive single use disposable components. In addition, these methods are often challenging to perform. The perforating veins typically are tortuous and short in length (e.g., between about 2 and about 7 cm), making the steps of needle access, positioning a laser fiber or RF catheter and injecting tumescent anesthesia technically difficult. And while foam sclerotherapy is relatively non-invasive, it is known to have a high rate of recurrence and potentially undesirable side effects. All of the methods generally require that the patient wear compression stockings for a period of about 1 to about 4 weeks post-procedure.
For those treatments that involve careful placement of a catheter at a particular intravenous treatment site, a reliable means for visualizing the instruments is needed. Ultrasound is a common method for device visualization in the medical device industry. Ultrasound works by emitting sound waves and analyzing the waves that are reflected and returned to the ultrasound sensing device. Despite its popularity, ultrasound visualization often provides inadequate resolution for careful intravenous placement of a catheter for the treatment of venous reflux disease, and improved echogenic catheters and methods of use are needed.